Plant Phenology

A series of images of aspen in different phenological stages.
A series of images showing aspen in different phenological stages--from winter dormancy to fall senescence.

NPS/Fleur Nicklen

Phenology is the study of the timing of biological events, such as when birds migrate north to breeding grounds or when leaves emerge on trees in the spring. Plant phenology in northern regions is often highly responsive to climatic variations and is one of the most sensitive indicators of climate change. There is considerable evidence that global climate change is advancing the timing of flowering and leaf-out and extending growing seasons of plants at northern latitudes and high elevations. A longer growing season has important consequences for plant growth and reproduction, plant-animal interactions like herbivory and pollination, and factors interacting with climate such as carbon exchange, albedo, and evapotranspiration. Understanding the exact cues triggering phenological events (temperature, snowmelt, photoperiod) is key to making accurate predictions about how individual species will respond to changing environments and understanding the consequences of the changes.

A defining characteristic of Central Alaska ecosystems is extreme seasonality: the presence of seasonal snow cover (currently) for about 8-9 months, and a compressed growing season of about 3-4 months. Seasonal snow cover defines the length of the growing season, is a major determinant of the annual water cycle, and greatly affects the reproduction and survival of animals. Within the snow-free season, the progression of vegetative development depends on climatic parameters including temperature, precipitation, and cloudiness (solar radiation).

The benchmarks in the annual development of seasonal snow cover and the vegetation canopy in Central Alaska parklands are: (1) snow-free date, (2) date of onset of greenness (“green-up” date), (3) date of maximum greenness, (4) date of senescence of greenness, and (5) snow-cover date.

We monitor plant phenology to better understand:

  • Are the dates of aspen flowering, leaf-out, and senescence changing over time?

  • What climatic variables are the most significant cues to aspen flowering, leaf-out, and

  • How does the phenology of aspen differ in different landscape positions and different locations in the Central Alaska Network?

We monitor plant phenology in all Central Alaska Network parklands.
Contact: Carl Roland


Find all articles, reports, and data here.


Learn more

Loading results...

    Last updated: June 15, 2018